this one may be a little crazy :)
the green version of the commuter both reg and superfast used a rivet to hold the glass to the underside of the roof. the red sf version eliminated the use of a rivet.
http://img64.imageshack.us/img64/6756/mercurycommutersf73glasar2.jpg
http://img63.imageshack.us/img63/8554/mercurycommutersf73glasht5.jpg
http://img75.imageshack.us/img75/9189/mercurycommutersf73glasac5.jpg

the three locations of the word mercury on the base plate of numbers 55 & 73. high touching top, between the top and slash lines and touching slash lines.
http://img258.imageshack.us/img258/834/55or73base1aw1.jpg
http://img258.imageshack.us/img258/5272/55or73base2gj9.jpg
http://img299.imageshack.us/img299/6238/55or73base3wh3.jpg

Mountain - do you have the lime version with wide wheels or the red version without the roof strips? These 2 both exist but are VHTF , although lime versions with enlarged wheel arches and skinny wheels are easy.Didnt Steve McQueen drive one of these in that classic old movie ´The Getaway´?
The most valuable normal issue SF Mercury of all is the 59 Fire Chief with skinny wheels VVHTF.The previous Galaxy was issued during the skinny wheels period, the Mercury Police sedan is common with skinny wheels but the Fire Chief :freak:

sms88-i have a few more lime green i can check for the wide wheels :)
the red without ribs and the 59 fire chief wide wheels do you know if these were a retail issued model?

there are two shades of red with the mercury fire chief too, can't see it too well in this picture and a 59 fire chief base plate with just 59
http://img459.imageshack.us/img459/6059/firechief59colorwq7.jpg
http://img459.imageshack.us/img459/9265/firechiefbasexl9.jpg

The red 73 without roof strips photo that I have seen was on a normal blistercard although it could be a color trial or fake car because none of the online big shot collectors have ever seen one of these in the metal.
Aparently the lime SF 73 with original wheel arches always have the gas filler cast but the widened arch lime cars never have the gas filler cast -do you have either of these possible so far unrecorded variations?
http://i38.photobucket.com/albums/e113/SMS369/toys/LS73a-03bxG.jpg
The skinny wheels 59 Mercury Fire Chief was a variation believed not exist until last year when a guy on mboxcommunity.com in London found one mint boxed ,posted a thread and only 1 other collector also had one - so perhaps this was a very limited release or they could be samples.
http://i38.photobucket.com/albums/e113/SMS369/toys/59firechief.jpg
http://i38.photobucket.com/albums/e113/SMS369/toys/59firechiefrivets.jpg With thanks to :wave: Jagman for the pix